The present invention relates to a wheel mounting apparatus for connecting a wheel including a wheel rim and a wheel disk to a vehicle axle. In particular, the present invention relates to a wheel mounting apparatus having a peripheral wheel mounting portion to be connected to the wheel, and having a hub mounting portion to be connected to a wheel hub, wherein the wheel mounting apparatus has a greater diameter than the wheel hub. Furthermore, the invention relates to a wheel mounting apparatus including such a wheel mounting apparatus integrally connected to a wheel hub.
The available free space under a wheel rim, regardless of the type of brake (drum or disk) used in the car, is used for dimensioning the wheel brake. Due to increased safety reserves for disk brakes of more recent design and, particular, those for use in the high temperature ranges, full utilization of the free space under a wheel rim for a 22.5 inch tire is not absolutely required. This is because, without sacrificing safety, it is possible to use smaller disk brake sizes over which a wheel rim for a 19.5 inch tire will also fit.
In order to cool the brake with air circulation, ventilation holes are commonly provided in the wheel disk between the wheel mounting portion and the wheel rim to allow air flow into the free space under the wheel rim. This type of cooling method for the brakes is necessary because high temperatures, particularly those on the inner wheel rim bead, could cause thermal damage to the tire in the area of the tire bead. In addition, wear of the brake linings at higher temperatures is greater than at lower temperatures.
In a wheel mounting portion for 19.5 inch tires on a pitch circle of 275 mm (a customary example), generously dimensioned ventilation holes can be provided without problems in the area of the wheel disk (which is less sharply oblique), because the distance between the wheel rim diameter and the pitch circle is sufficiently large for the wheel mounting portion. Therefore, ventilation problems are minimized for this design.
However, for a 19.5 inch tire with a wheel mounting portion on a pitch circle of 335 mm (which is customary for 22 inch wheels), there are difficulties in accommodating the ventilation holes in the wheel disk. Due to the size of the pitch circle, only relatively small ventilation holes can be provided in the oblique region of the wheel disk which, due to their oblique position, are further reduced in effectiveness. Thus, in wheel mounting combinations having small wheel rim diameters and large pitch circles, the relatively small radial spacing between the wheel rim and pitch circle creates ventilation problems.
Therefore, one object of the present invention is to provide a wheel mounting apparatus which allows improved ventilation of the brakes regardless of the wheel rim size and the diameter of the pitch circle. For example, the wheel mounting apparatus of the present invention provides improved ventilation for a standard pitch circle diameter for a wheel mounting of 335 mm. The object of the present invention is achieved by providing a wheel mounting apparatus similar to the general type described above, in which ventilation passages are formed between the wheel mounting portion and the flange mounting portion.
Although the areas of the wheel mounting portion of the wheel mounting apparatuses are especially subject to stress, it was found that when satisfactory stability of the wheel mounting apparatus is maintained, it is possible to provide ventilation passages through which, even when there is a small space between the wheel mounting portion and the wheel rim, a sufficient quantity of air can flow under the wheel rim. Thus, the heat generated during braking can be effectively dissipated. Due to the location of the ventilation passages in the region between the wheel mounting portion and the hub mounting portion, the cooling air can flow into the wheel mounting apparatus better than through ventilation holes that are disposed in an already oblique region of the wheel disk, because these holes are partially covered by the outer wheel rim bead of the wheel rim.
Therefore, due to the arrangement of the present invention, a substantially improved heat dissipation from the brake is achieved. Moreover, even for smaller 19.5 inch wheels, a wheel mounting portion having a larger pitch circle (for example, 335 mm) can be used. Thus, the wheel mounting apparatus can be universally used for different brakes for 19.5 inch and 22.5 inch wheels (wheel rims). This allows a reduction in the fabrication costs, and a reduction in the requirement of fabricating multiple parts.
The ventilation passages, openings, or recesses in the periphery of the wheel mounting apparatus of the present invention also simplify the casting process during production, because the molding sand for setting up the casting mold can be injected better.
The cooling effect on the brakes can be further augmented by providing ventilation holes in the wheel disk. In addition, further cost savings and cooling effect can be achieved by providing ventilation passages so that only spoke-shaped connection webs remain between the ventilation passages. These connection webs can be developed so that they are oblique and/or they are in the form of arcs in order to direct air towards the brake to achieve an improved ventilator effect. For an optimum ventilator effect, the connection webs can be formed so that their outer edges are oblique with respect to a rotation direction of the wheel. In other words, the outer sides of the connection webs extend or project in a direction of rotation of the wheel as the vehicle moves forward.
According to a further embodiment of the wheel mounting apparatus of the present invention, the ventilation passages can be developed as radial opening or as oblong holes having major axes which are arranged in the circumferential direction of the wheel mounting apparatus.
In order to achieve a uniform cooling effect, the ventilation passages may be distributed uniformly on the surface of the wheel mounting apparatus. For example, the ventilation passages may be arranged on one or several pitch circles.
In one embodiment of the wheel mounting apparatus of the present invention, the wheel mounting portion and the flange mounting portion are located in different vertical planes and are connected to one another by an oblique connection section. In this embodiment, the ventilation passages are located in the oblique connection section. Thus, if the wheel mounting portion projects axially outward (with respect to the vehicle axial) relative to the hub mounting portion, a particularly simple connection between the wheel and the wheel mounting apparatus is possible.
Through-holes for receiving wheel bolts are preferably used in order to mount the wheel mounting apparatus onto a wheel. In order to achieve further weight savings and a further simplification of the casting process, additional ventilation holes can be provided near the outer periphery of the wheel mounting apparatus. For example, radially-arranged oblong holes or recesses can be provided near and/or between the through-holes.
To prevent turning of the wheel bolts that connect the wheel mounting apparatus to the wheel, the bolt head of the wheel bolt can preferably have a flattened portion which is braced against a collar on the wheel mounting apparatus. This collar also widens the wheel mounting apparatus and, therefore, improves rigidity and strength of the wheel mounting apparatus.
The through-holes for the wheel bolts may also have, at least on one side, an oblique edge (i.e., rounded-off or chamfered, but not square). This oblique edge of the through-holes prevents xe2x80x9ctechnical notchesxe2x80x9d which reduce the operational strength of the wheel mounting apparatus by creating an increased stress point, but the oblique edges do not decrease the rigidity of the wheel mounting apparatus.
In one embodiment of the present invention, a brake disk can be mounted to the wheel mounting apparatus by the bolts which connect the hub mounting portion of the wheel mounting apparatus to the wheel hub. In this first embodiment, the wheel hub is provided as a separate structural component, preferably as a cast metal portion, and is connected to the hub mounting portion.
In a second embodiment of the present invention, the wheel mounting apparatus includes a wheel hub in the area of the hub mounting portion of the first embodiment. The wheel hub in this embodiment is integrally connected to the wheel mounting portion. Thus, the wheel mounting apparatus does not include a hub mounting portion. In other words, the wheel mounting portion is integrally connected to the wheel hub (i.e., not mechanically fastened by bolts). In this case, the ventilation passages in the wheel mounting portion provide additional benefits during the casting (production) process for the wheel mounting apparatus. Specifically, molding sand can be injected at a very high velocity and can pass through the ventilation passages in order to set up the mold for the brake disk which is to be cast in a compound casting. For this purpose, the integral and precast wheel hub and wheel mounting portion is jointly placed into the second mold. The same casting technological advantage is also provided by additional through-holes or recesses in the periphery of the wheel mounting apparatus. In a preferred arrangement of this embodiment, a brake disk is developed as a compound cast part, and formed integrally with the wheel hub and axially spaced apart from the wheel mounting portion.